Where does steel come from - Overview steel making process

Steel is commonly used in various industries but have you ever wondered where does steel come from and the origins of this material?

In today's article, let's delve deep into the steel production process, the raw materials involved, and the factors influencing the process. Through this exploration, we aim to gain a better understanding of the role of steel in the current economy. Join us at MRS Steel for this insightful journey!

Iron ores must undergo six main stages to form the final steel product

What is steel made of - the raw material for manufacturing of steel

To answer the question of where does steel come from, considering the various aspects of chemistry is unavoidable. Specifically, all alloys in steel are predominantly iron, with carbon content ranging from 0.02% to 2.1% by weight, a ratio that plays a crucial role in determining the properties of the steel product.

Within the realm of molecular structure, carbon forms a robust microstructure network when bonded with iron to steel, thereby contributing significantly to the enhancement of the hardness. Furthermore, the adjustment of carbon content in steel directly influences various other properties such as strength, ductility, and load-bearing capacity. The synergistic combination of iron and carbon renders steel an extraordinarily diverse material, capable of fulfilling specific requirements across various industrial applications.

Although the majority of steel comprises iron and carbon, it also contains small percentages of other elements such as nickel, molybdenum, manganese, titanium, boron, cobalt, or vanadium. For example, nickel is often used to produce stainless steels, with nickel content reaching up to 10.5% in some cases.

Iron ores is the main raw material for question where does steel come from

Properties of iron to steel and how is steel made from iron

In nature, iron ore typically contains various impurities such as silica, phosphorus, and sulfur. These impurities can weaken iron and indirectly affect the quality of steel in production. Therefore, in the early stages of the steel making process, manufacturers undertake steps to remove these impurities from the iron to produce purer iron ore. Subsequently, carbon is added to create various types of steel with desired mechanical and physical properties.

Typically, the melting temperature of iron in the manufacturing of steel ranges from approximately 1,370 to 1,540 degrees Celsius (2,500 to 2,800 degrees Fahrenheit). Such high temperatures are deemed necessary to melt iron and facilitate the removal of impurities and other additives by manufacturers. When iron is heated to its melting point, impurities such as silica, phosphorus, sulfur, and other additives separate and are eliminated, resulting in purer molten iron.

Manufacturers will remove these impurities from the iron to produce purer iron ore

6 main stages in steel making process

Have you ever wondered about how to make steel or how steel is formed within a manufacturing facility? The journey from iron to steel product is a multifaceted process that comprises six primary stages. These stages include making the iron, primary steelmaking, secondary steelmaking, casting, primary forming, and secondary forming.

Making the iron to steel

The first step in the steel making process is the ironmaking stage, a crucial step to convert iron ore into pig iron. Pig iron has distinct properties compared to raw iron because it contains more carbon, with the carbon components serving to harden the pig iron and facilitate reactions with other substances.

This initial stage occurs in blast furnaces, where iron ore is introduced and processed with other materials such as coke and limestone. Through the combination of fuel and extremely high temperatures in the furnace, chemical reactions take place to remove unwanted impurities such as silica, phosphorus, and sulfur.

The pig iron is then collected and transferred to the second stage of the manufacturing of steel to further transform it into the final steel products. It can be observed that the ironmaking stage is a crucial determinant in ensuring the quality of the steel later on by increasing the purity of the raw material. Additionally, the carbon content in pig iron can be adjusted at this stage to control the mechanical properties of the steel as desired.

The ironmaking stage will convert iron ore into pig iron to remove impurities

Primary steelmaking

In the primary steelmaking step, the pig iron will be fed into a steelmaking furnace, typically either a Blast Furnace (BOF) or Electric Arc Furnace (EAF), along with other materials such as coke and limestone. Both types of steelmaking furnaces operate differently and have distinct requirements. In the furnace, the pig iron is melted at extremely high temperatures, usually above 1,500 degrees Celsius, to further separate carbon and other impurities from the pig iron.

In the Basic Oxygen Furnace (BOF), the pig iron is transferred into the furnace through a duct system along with a large volume of air blown, including oxygen-containing substances such as liquid oxygen or oxygen gas. At this point, oxidation reactions occur between the components in the pig iron and the oxygen gas, contributing to increased temperature and the production of carbon monoxide gas.

In the BOF, the pig iron is transferred with a large volume of oxygen

Conversely, in the Electric Arc Furnace (EAF), the primary materials include pig iron and scrap steel. A negative electrode is inserted into the furnace, creating a positive electrode in the molten steel, and an electric current provides enough heat to melt the pig iron and scrap steel. During this making steel process, impurities such as silicon, manganese, and other metals are melted and removed from the steel.

After the reaction refining process is completed, the liquid steel is cooled to control its crystalline structure and mechanical properties. This process may involve using cooling methods such as quenching (rapid cooling) or controlled cooling.

Specifically, in the quenching process, the liquid steel is rapidly cooled by immersing it into a cooling liquid such as oil or water. Similarly, with the controlled cooling method, the cooling process is adjusted and tightly regulated within a controlled environment to ensure that there are no abrupt changes in its structure. In some cases, manufacturers may opt to cool the liquid steel by simply allowing it to gradually cool down naturally in the air.

Electric Arc Furnace (EAF) will create a positive electrode in the molten steel

Secondary steelmaking

If the goal of the primary steelmaking process is to remove impurities and adjust the carbon content of the steel, then the secondary steelmaking process will focus primarily on refining the crystalline structure and properties of the steel through the use of additives. At this stage, the liquid steel from the primary steelmaking furnace is transferred to the secondary steelmaking furnace to undergo chemical reactions aimed at adjusting the carbon content.

Once the steel has been refined by the manufacturer to achieve the appropriate mechanical structure, it undergoes further cooling, during which the manufacturer may add additional additives such as nickel, molybdenum, and manganese to enhance strength, hardness, and corrosion resistance in the steel. Throughout the process, strict quality control measures are implemented by the manufacturer to ensure that the final product meets the required standards and technical specifications.

The secondary steelmaking process refines the steel's crystalline structure by using additives

Casting

The overview of the entire process to uncover “where does steel come from” is now halfway complete. In the fourth step of the steel making process, the molten iron mixture is now transferred from the smelting furnace into molds via a guiding system to ensure the final product will have the desired shape and dimensions. The molds within the factory are made from special steel or materials capable of withstanding the high temperatures of molten iron.

Once the entire molten iron is poured into the molds, the cooling process begins. During this period, the steel gradually solidifies to form the final product. However, for steel products that require high precision in dimensions or mechanical properties, the cooling process may involve cooling methods such as water or air cooling, with temperature adjustments as needed.

The molten iron is poured into molds to achieve the desired shape for the final product

Primary forming

It can be observed that when steel transitions from the casting process, it takes on specific shapes such as plates or square ingots. Upon reaching this point, one might wonder: how steel is formed according to specific customer requirements in further processing? Let's delve into the following lines!

Once the cooling process is complete, the steel products are taken out of the molds and proceed to undergo basic shaping processes as well as initial forming through methods like laminating, rolling, or forging.

Laminating process

Specifically, in the laminating process, raw steel plates are fed through thinning machines to reduce their initial thickness, which may involve pressure rollers or press machines. Throughout the thinning stage, manufacturers adjust pressure and temperature to ensure uniform deformation of the steel plates. 

Rolling process - one of the most popular manufacturing of steel

Another fundamental shaping stage worth mentioning is the rolling process, where raw steel plates are fed through rolling mills to create basic-shaped products such as flat sheets, beams, tubes, or steel wires. Rolling mills consist of a series of rollers or rolling shafts arranged in sequence to apply pressure to the steel plates and begin to deform the steel surface.

Forging process

The forging process takes a different approach compared to the previous two processes, as the steel is heated in a furnace to the necessary temperature to transition from a solid to a liquid state. This creates ideal conditions for the steel to easily deform under high pressure from forging machines. In summary, the Forging process is typically used to produce steel products with complex shapes and high precision requirements such as machine parts or components.

Steel products will go through basic shaping in primary forming step

Secondary forming - the final steel in steel making process

The secondary forming process is the final stage in the steel production process to complete the overall picture of “where does steel come from”. Here, steel products from the primary shaping stage are further processed to meet specific customer requirements. Some common processing steps in this process include mechanical processing, welding, cutting, and galvanizing.

Mechanical processing in making steel

Mechanical processing typically involves several methods such as grinding, drilling, bending, or using CNC machines to create products with desired dimensions and shapes. In the welding method, steel components and parts are joined together by using high temperature to melt the base material and welding material, creating a molten solution, and when they cool down, they form a strong bond.

Cutting methods

The cutting method is utilized to cut and form steel plates into custom sizes with the assistance of various equipment such as plasma cutters, laser cutters, or mechanical cutting machines. Besides that, one of the most common processing methods in enhancing the durability of steel is galvanization. A layer of zinc coating can be applied to the surface of steel using various methods, including hot-dip galvanizing, electroplating, or zinc spraying.

Through the secondary shaping process, steel products are transformed from flat or square shapes into specific forms such as pipes, wires, steel cords, or other complex-shaped products. In addition to shaping, the application of pressure or controlled cooling can improve the mechanical properties and structure of steel products.

The steel products will be finished through mechanical processing, welding, cutting, and galvanizing methods

Learn more about steel industry perspective with MRS Steel

In general, to answer the question where does steel come from, we need to understand the entire process of its metallurgy and processing to recognize that manufacturing of steel is a technical step that requires strict precision and expertise. Each stage in the process plays a crucial role in the chain of operations, from removing impurities in steelmaking to shaping in the primary stages and adjusting the final product.

Through this article, MRS Steel hopes that readers will gain a deeper insight into the six processes in today's factories to clarify “how is steel made from iron?”. Currently, MRS Steel is a provider of steel solutions for importers in the Vietnamese market. If you have any inquiries about our products, please feel free to contact us via WhatsApp: +84 769 112 358 or email: vanloc@mrssteel.com.vn.